The Causes of Septic System Drainfield or Soakaway Bed Failure

SEPTIC FIELD FAILURE CAUSES - CONTENTS: Causes of septic system drainfield or leachfield failures, how to recognize & diagnose failing conditions in a septic field. Definitions of septic failure for each component

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What causes a septic system failure?

This septic system diagnosis article explains the causes of septic system failure in the drain field, leach field, seepage bed, or similar
component. We list the causes of each type of septic component failure, and list the septic component failure criteria
or in other words what conditions are defined as "failure"? We also discuss what can be planted over and near a septic drainfield and what should be avoided.

How can you distinguish between a blocked pipe, a septic tank that
needs pumping, and a clogged drainfield that needs replacement? This is an important question as it distinguishes between relatively
low cost maintenance or repair task and a costly septic leach field replacement.

Here is a list of the causes of sewage wastewater disposal field failures. These factors explain why soakaway beds, seepage beds, leach fields, disposal fields, drainfields, or other synonymous effluent treatment & disposal systems fail early or at the end of a normal life.

Septic Drainfield Age: eventually even a well-maintained SAS will eventually clog and have to be replaced.

Just how quickly depends on several factors including original construction type, materials, and quality, field size, septic system usage level, soil characteristics, soil water or groundwater control, and of course septic tank pumping frequency to avoid sending solids into the fields.

But for all systems that depend on disposal and treatment of wastewater in the soil, the biomat that forms around drainage trenches, seepage beds, or soakbeds, cesspools and soakpits eventually clogs.

In Causes and remedy of failure of septic tank seepage systems. [PDF] Harkin explains simply:
The reason for [septic absorption ] system failure is the gradual formation underground of an imperable clogged or crusted layer in the soil blow and surrounding the seepage bed. Flow of water through this clogged or crusted zone is severely restricted or even eliminated, although the permeability of the surrounding soil remains essentially unchanged. Consequently, huge voumes of stagnant septic tank effuent accumulates in the seepage bed. -
Harkin (1975)
See SEPTIC DRAINFIELD LIFE

Nevertheless a number of additional factors can hasten the demise of a septic soakbed or leachfield.

Septic Tank Pumping schedule: don't forget to pump out the septic tank regularly (solids/grease are discharged into the fields, clogging the soil).

Soil clogging at the biomat layer which forms below and around the drainfield trenches (or other absorption systems).
The biomat is a bacteria layer which forms in soil below and around drainfield trenches where septic effluent or wastewater
is discharged.

This biomat layer is critical in the processing of fine biological solids and pathogens which are in the effluent, and
without it the septic system would not be adequately treating the effluent. Inadequately-treated effluent released into the ground
risks contamination of nearby ponds, wells, streams, etc.

Septic Tank Baffle failures: corrosion and rust-off of steel septic tank baffles is a significant cause of disposal field failure in systems that have otherwise been maintained by proper tank pumping schedules. Concrete or plastic tank baffles also fail, break, or fall off; baffles can be repaired or replaced but the drainfield may already have been damaged and its future life reduced.
See SEPTIC TANK BAFFLES for details.

Blocking or sealing the ground surface over a septic drainfield will be a problem over just about
any septic effluent absorption field. Don't build anything over a
septic mound, no building, no fish pond, no patio, no tennis court, no
parking area, no playground (compacts the soil).

Don't put a swimming pool on top of a drainfield - yes I've seen people do this including my neighbor! See the photo at the top of this page.

Don't put a concrete block pation on top of a septic drainfield

Don't pave over the septic drainfield

Don't put outdoor carpeting over a septic drainfield

Don't install astroturf™ or other synthetic groundcovers over a septic drainfield unless a careful review with the product manufacturer assures that the cover will not interfere with moisture evaporation from the soil below and oxygen entry into the soil below

Don't build a building or deck on top of the septic drainfield - you risk damaging the drainfield during construction by equipment, by breaking pipes, by digging into a pipeline, and you prevent future access and repair to the drainfield

Don't seal the drainfield or soakaway bed top from contact with air by leaving a plastic liner of any sort - ice rink, swimming pool, tents and tarps in place. Temporary placement of such sealers, depending on weather conditions and temperatures, may not be harmful, such as during solid freezing conditions, but we have not found independent research that confirms or denies the problem. For example, details of the pros, cons, & warnings about building a temporary ice rink over septic fields are found at ICE SKATING OVER SEPTIC

Driving vehicles or any heavy equipment over the absorption system, leach field, drainfield.
As with any septic absorption system, heavy traffic over the
system can compress soil or break pipes, rendering the system inoperative
and requiring costly repairs.

At a recent inspection I found that the
septic mound had been placed over a roadway connecting two properties
owned by the same family. Family members continued to drive back and
forth between homes right over the septic mound. Its future life was
rather doubtful.

Driving vehicles over the septic mound or other
drainfield, even for a single project such as construction of a nearby
structure or performing other site work, is likely to damage the system
and lead to need for costly repairs.

Kahn et als. also advise keeping
grazing animals, horses, cows, etc. off of mound systems.
In the photo shown here, light snow makes it quite apparent where someone has
been driving through this field. Compacting the soil by driving over the
drainfield will damage it and may lead to early failure.Details are at DRIVING or PARKING OVER SEPTIC

Septic tank converstion to aerobic or aerator systems without proper design, components, or installation. Simply dropping an aeration system into a conventional septic tank, particularly a single-chamber septic tank will virtually guarantee that suspended solids will be sent into and then destroy the leaching fields. Settlement chambers, septic filters or an equivalent will be needed when converting from a conventional to an aerobic septic system design.
See CONVERT to AEROBIC SEPTIC SYSTEM

Inspecting raised bed and mound systems in New York State I have often seen improperly
constructed mounds including efforts by the builder to save on fill cost
by using the "mound" as a place to first pile up all of the trees and
tree stumps which needed to be cleared from the site, covering this mess
with a too-thin layer of fill soil in which the septic absorption
trenches are installed.

The result is a mound system with a short life.
If you see trees poking out from the perimeter of your mound further
investigation may be in order. Also watch for effluent breakout around
the bottom edges of the mound.

Driving over the septic drainfield trenches during construction, omitting the required gravel under and around drainfield trench piping, and possibly backfilling with heavy wet clay-based soils during construction may also damage the field or reduce its performance.

Houses clustered around a lake: often will have a marginal system as properties were crowded
together, built as part-time summer-camps, were built without code supervision, and often were built using amateur, marginal home-made systems.

In our photograph (left), new construction placed the septic tank and septic drainfields in the wet area shown in the photo.

Everything looked questionable: the drainfield is placed near trees, risking root invasion of the piping; the drainfield is placed in
wet soils, and the total elevation between the bottom of the drainfield piping and the top of the nearby lake is less than two
feet. The drainfield is placed less than 20 ft. from the edge of the lake.

It is improbable that the septic system belonging to this property will do much more than contaminate the nearby lake.

Improper septic absorption field location:
one way to have a quick failure of a drain field is to
install it in an area of high seasonal water tables (flooding the system) without
sufficient fill and elevation, and/or without providing extra site and intercept
drainage around the field to keep surface and subsurface water away from the field.

Surface & subsurface runoff water control mistakes: Ignoring site runoff and groundwater levels:
Improper absorption field siting is found at some properties where the builder
fails to consider site runoff or natural groundwater paths. One mound
system was constructed using too little fill and placed over what had
been a stream bed.

My septic dye test very quickly produced red-dyed
effluent at the low end of the mound where a seasonal stream continued
to run under the mound in wet weather.
Flooding the absorption system with surface or roof runoff, or rocky, poorly-drained or under-sized
sites may simply lack capacity means a short absorption field life.

Steep slope septic systems: Placing a conventional
septic system drainfield on a steep slope, over a stream bed, over
a natural drainage swale (photo of this defect), specifying an
under-sized mound or raised bed for the anticipated usage level, and poorly installed
piping which does not slope properly or which becomes disconnected, and
finally, use of improper fill soil which lacks the proper percolation rate
all result in a costly installation with a too-short life.

Sloppy pipe layout and connections is a common cause of early failure in new
drainfields. Pipes placed in trenches at uneven slope become disconnected; trenches with improper
slope and omission of
the specified amount and improper placement of gravel (for those systems) are also quite common where
there is time or money pressure working against the builder.

Placing structures, patios, or paving over the absorption system:
Covering an absorption bed, raised bed, or septic mound, such as by
installation of paving, a patio, or weed-blocking solid plastic, will
damage the mound and prevent proper operation by blocking both oxygen
intake into the soil and also evaporation of effluent from the soil top. See "Blocking the ground" earlier in this list.

Placing improper substances into the building drains and septic system. Don't
use the septic system to dispose of illegal oils, chemicals, fats, greases. One system in New York near the Taconic State Parkway
was connected to house in which was operated an illegal drug manufacturing operation. So much contaminant was flushed down house drains
that the workers contaminated their own well and poisoned themselves.
See TOILETS, DON'T FLUSH LIST

Planting trees, deep rooting shrubs, and certain ground covers on the septic absorption field (roots enter pipes)
and evaporation can be blocked.
See SEPTIC SYSTEMS, PLANTS OVER

Use of septic tank or drain field additives which claim to extend system life can generate so much activity in the tank that
solids are held in suspension and forced into the soil absorption system! Do
not add any treatments, chemicals, yeast, or other treats to a septic system. In general these treatments don't work, may ruin the system, and
are illegal in many localities. There is no magic bullet to repair a bad SAS.
See SEPTIC TREATMENTS & CHEMICALS

Wet weather installations of septic systems & fields: Installing a drainfield in wet weather (which compacts the soil) is likely to
mean a shorter field life.

Frequently Asked Questions (FAQs)

Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.

Question:
state road work causes problems for drainfield?

(Aug 29, 2014) Dawn said:
Many years ago our parents sold approximately 40 feet of the west end of our home's property so that the state could put in a frontage road. The soil that was brought in to raise the frontage road about 6 feet above the land's original elevation and a culvert that was installed under that frontage road appears to have blocked the drainage of our property. Is that possible? Our septic drain field, located within the area that is now flooding frequently, is therefore not working correctly. The state has been contacted about whether the culvert is set too high to allow our property to drain, but they say that is no problem. Any advice on how to get the state's attention? It seems to me that by blocking our property with a six foot berm topped by a frontage road and installing a culvert that doesn't drain the property would cause the septic drain field to become saturated by rainwater and is causing our problem of a wet drainage field, but I'm no engineer.

Reply:

Dawn you may be correct IF the blockage leaves an accumulation of surface runoff atop your drainfield, or mistaken if the drainfield is saturated because of other failure causes. You may want to hire a local septic engineer or civil engineer to inspect the site, diagnose the drainage issue, prepare appropriate drawings and a report on proper remedy.

Keep us posted

Question: plans to zero-scape our yard with Egg Rock

(Oct 3, 2014) Davis said:
I live in South Florida with very sandy soil. My Wife and I want to zero scape our yard with Egg rock. We have a 22' X 25' drain field in the area we we want to place the rock. Any ideas about placing about 2" of rock over the field.
Thanks. David

(Oct 13, 2014) David said:
Would like to place an inch or two of egg rock over my drain field, will this hurt the drain field in any way? This is sandy soil,in full sun most of the year, and there will only be wheel barrow traffic on it until the rock is spread. This is about 500 sf of drain field, 22x25. Installed in 2013. Thanks

Reply:

Davis

What I'd be nervous about is driving equipment over the septic field, destroying it.

We replied to this elsewhere as well as by email. Driving equipment over the field to place rock risks damaging it. But gentle hand work as described should not. Finally, however, removing grass covering reduces the soil transpiration and moisture uptake rate so might reduce the fields ability to dispose of effluent.

(Oct 7, 2014) Anonymous said:
No driving of equipment over the field, just a wheel barrow. Will placing about 1 1/2 to 2" of egg rock compromise the field in any way?

Oct 19, 2014) Anonymous said:
There is currently no grass over the field, just sand. I think we will plant a garden of some sort over the field. Flowers and such, nothing edible . Again thank you for your help.
David

Reply:

Sounds as if you're ok. An authoritative answer would, of course, come from the design engineer to designed the specific septic system in question as s/he would know the details.

Question: ok to store a boat over the septic field?

Reply:

Anon: a boat supported on a dolly, if it is not heavy enough to crush soils or drainfield trenches, would not be likely to be a problem, but driving onto the fields to park or remove the boat could damage the fields.

Question: what do you do when you have a seeping drain field?

Judy said:

what do you do when you have a seeping drain field?

Reply:

Judy:

Pumping the septic tank MIGHT give a few days (not more) of relief and slow the seepage down in some cases but not all of them. You need an on-site septic expert to diagnose the trouble an d then give recommendations on repair. The possible causes are varied, as the article above notes.

Question: I want to fix the drainfield with chemicals

Can't I just pour a drainfield restorer chemical into the toilet to fix the seeping drainfield?

Reply:

Vicki:

While there are treatments sold that purport to cure or restore a failed drainfield, after years of work in this area I've yet to find an independent research study that confirmed that they actually work reliably; worse, some treatments are toxic or caustic and harmful to the environment - and thus are illegal to use in most jurisdictions.

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Harkin, John M., Michael D. Jawson, and F. G. Baker. Causes and remedy of failure of septic tank seepage systems. [PDF] University of Wisconsin, 1975.
This text explains the reasons for soil clogging and septic drainfield failure. - Ed.The reason for [septic absorption ] system failure is the gradual formation underground of an imperable clogged or crusted layer in the soil blow and surrounding the seepage bed. Flow of water through this clogged or crusted zone is severely restricted or even eliminated, although the permeability of the surrounding soil remains essentially unchanged. Consequently, huge voumes of stagnant septi tank effuent accumulate in the seepage bed.

Soil Test Pit Preparation, fact sheet, Oregon DEQ Department of Environmental Quality, original source www.deq.state.or.us/wq/pubs/factsheets/onsite/testpitprep.pdf The Oregon DEQ onsite water quality program can be contacted at 811 South Ave, Portland OR 97204, 800-452-4011 or see http://www.oregon.gov/DEQ/

Document Sources used for this web page include but are not limited to: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and
Kelli S. Martin. Penn State College of Agriculture - Cooperative Extension, edited and annotated by
Dan Friedman (Thanks: to Bob Mackey for proofreading the original source material.)

Advanced Onsite Wastewater Systems Technologies, Anish R. Jantrania, Mark A. Gross. Anish Jantrania, Ph.D., P.E., M.B.A., is a Consulting Engineer, in Mechanicsville VA, 804-550-0389 (2006). Outstanding technical reference especially on alternative septic system design alternatives. Written for designers and engineers, this book is not at all easy going for homeowners but is a text I recommend for professionals--DF.

Builder's Guide to Wells and Septic Systems, Woodson, R. Dodge: $ 24.95; MCGRAW HILL B; TP;
Quoting from Amazon's description: For the homebuilder, one mistake in estimating or installing wells and septic systems can cost thousands of dollars. This comprehensive guide filled with case studies can prevent that. Master plumber R. Dodge Woodson packs this reader-friendly guide with guidance and information, including details on new techniques and materials that can economize and expedite jobs and advice on how to avoid mistakes in both estimating and construction. Chapters cover virtually every aspect of wells and septic systems, including on-site evaluations; site limitations; bidding; soil studies, septic designs, and code-related issues; drilled and dug wells, gravel and pipe, chamber-type, and gravity septic systems; pump stations; common problems with well installation; and remedies for poor septic situations. Woodson also discusses ways to increase profits by avoiding cost overruns.

Country Plumbing: Living with a Septic System, Hartigan, Gerry: $ 9.95; ALAN C HOOD & TP;
Quoting an Amazon reviewer's comment, with which we agree--DF:This book is informative as far as it goes and might be most useful for someone with an older system. But it was written in the early 1980s. A lot has changed since then. In particular, the book doesn't cover any of the newer systems that are used more and more nowadays in some parts of the country -- sand mounds, aeration systems, lagoons, etc.

Design Manuals for Septic Systems

US EPA Onsite Wastewater Treatment Systems Manual [online copy, free] Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm Onsite wastewater treatment and disposal systems,
Richard J Otis, published by the US EPA. Although it's more than 20 years old, this book remains a useful reference for septic system designers.
U.S. Environmental Protection Agency, Office of Water Program Operations; Office of Research and Development, Municipal Environmental Research Laboratory; (1980)

Onsite Wastewater Disposal Books

Onsite Wastewater Disposal, R. J. Perkins;
Quoting from Amazon: This practical book, co-published with the National Environmental Health Association,
describes the step-by-step procedures needed to avoid common pitfalls in septic system technology.
Valuable in matching the septic system to the site-specific conditions, this useful book will help you install a reliable system in
both suitable and difficult environments. Septic tank installers, planners, state and local regulators, civil and sanitary engineers,
consulting engineers, architects, homeowners, academics, and land developers will find this publication valuable.

Onsite Wastewater Treatment Systems, Bennette D. Burks, Mary Margaret Minnis, Hogarth House 1994 - one of the best septic system books around, suffering a bit from small fonts and a weak index. While it contains some material more technical than needed by homeowners, Burks/Minnis book on onsite wastewater treatment systems a very useful reference for both property owners and septic system designers.

Septic System Owner's Manual, Lloyd Kahn, Blair Allen, Julie Jones, Shelter Publications, 2000 $14.95 U.S. - easy to understand, well illustrated, one of the best practical references around on septic design basics including some advanced systems; a little short on safety and maintenance. Both new and used (low priced copies are available, and we think the authors are working on an updated edition--DF.
Quoting from one of several Amazon reviews: The basics of septic systems, from underground systems and failures to what the owner can do to promote and maintain a healthy system, is revealed in an excellent guide essential for any who reside on a septic system. Rural residents receive a primer on not only the basics; but how to conduct period inspections and what to do when things go wrong. History also figures into the fine coverage.

Grass is Always Greener Over the Septic Tank, Bombeck, Erma: $ 5.99; FAWCETT; MM;
This septic system classic whose title helps avoid intimidating readers new to septic systems, is available new or used at very low prices.
It's more entertainment than a serious "how to" book on septic systems design, maintenance, or repair. Not recommended -- DF.

US EPA Onsite Wastewater Treatment Systems Manual Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm

Water Wells and Septic Systems Handbook, R. Dodge Woodson. This book is in the upper price range, but is worth the cost for serious septic installers and designers.
Quoting Amazon: Each year, thousands upon thousands of Americans install water wells and septic systems on their properties. But with a maze of codes governing their use along with a host of design requirements that ensure their functionality where can someone turn for comprehensive, one-stop guidance? Enter the Water Wells and Septic Systems Handbook from McGraw-Hill.Written in language any property owner can understand yet detailed enough for professionals and technical students this easy-to-use volume delivers the latest techniques and code requirements for designing, building, rehabilitating, and maintaining private water wells and septic systems. Bolstered by a wealth of informative charts, tables, and illustrations, this book delivers:* Current construction, maintenance, and repair methods
* New International Private Sewage Disposal Code
* Up-to-date standards from the American Water Works Association

Wells and Septic Systems, Alth, Max and Charlet, Rev. by S. Blackwell Duncan, $ 18.95; Tab Books 1992. We have found this text very useful for conventional well and septic systems design and maintenance --DF.
Quoting an Amazon description:Here's all the information you need to build a well or septic system yourself - and save a lot of time, money, and frustration. S. Blackwell Duncan has thoroughly revised and updated this second edition of Wells and Septic Systems to conform to current codes and requirements. He also has expanded this national bestseller to include new material on well and septic installation, water storage and distribution, water treatment, ecological considerations, and septic systems for problem building sites.

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